1. Technical Field
The present disclosure relates to a carbon nanotube array structure and a method for making the same.
2. Description of Related Art
A carbon nanotube array can be grown on a flat silicon wafer by a chemical vapor deposition (CVD) method. More specifically, a layer of nanosized catalyst grains is arranged on the flat silicon wafer by annealing a metal film deposited on the wafer. The wafer is then heated in a reactor chamber. Carbon source gas and protective gas are introduced into the reactor chamber and the carbon source gas is pyrolyzed by an action of the catalyst grains at elevated temperature to grow the carbon nanotube array on the flat silicon wafer. However, the area of the flat silicon wafer is restricted by the size of the reactor chamber, accordingly, the area of the carbon nanotube array grown on the flat silicon wafer is restricted by the area of the flat silicon wafer.
Recently, a method for growing a large-area carbon nanotube film is disclosed by the patent application US20070292614 A1 to Liu et al. The method includes steps of:
providing a rigid substrate with a curved surface;
forming a catalyst layer on the curved surface of the substrate;
fixing the substrate in a reactor chamber; and
growing a carbon nanotube film on the curved surface of the substrate by the CVD process.
A shape of the curved surface of the substrate can be cylindrical, helical, or another shape. The flat silicon wafer and the substrate with the curved surface can be accommodated in the same reactor chamber, and can have different surface areas for the carbon nanotubes to grow thereon, wherein the curved surface of the substrate is larger than the flat surface of the flat silicon wafer. Therefore, a larger carbon nanotube film can be achieved by using the substrate with the curved surface without increasing the size of the reactor chamber or a diameter of a tube furnace.
However, in the above method, the substrate with the curved surface is made of a rigid material. Compared with the carbon nanotube array grown on the flat silicon wafer, the carbon nanotube film grown on the curved surface of the substrate is not convenient to be used in practice. For example, the carbon nanotube film grown on a central portion of a helical shaped substrate is difficult to be used.
What is needed, therefore, is to provide a carbon nanotube array structure with a large area and a method for making the same, wherein the carbon nanotube array structure is convenient to be used.